Molten slags include, for example, molten blast furnace slag, molten converter slag, and molten electric furnace slag. It is known that it is possible to obtain a vitreous slag by cooling a molten slag mentioned above at a high cooling rate for solidification.
FIGS. 1 and 2 illustrate an apparatus for manufacturing a vitreous slag, which is substantially the same as the apparatus for manufacturing a vitreous blast furnace slag disclosed in Japanese Patent Provisional Publication No. 11,154/80 dated Jan. 25, 1980. FIG. 1 is a schematic front view illustrating an embodiment of the apparatus for manufacturing a vitreous slag. FIG. 2 is a sectional view of FIG. 1 cut along the line A--A'. In FIG. 1, 1 is an endless conveyor belt; 2 are a pair of sprocket wheels for travelling the endless conveyor belt 1; and 4 are a plurality of rectangular cooling metal members forming the endless conveyor belt 1 by being connected to each other. At least one sprocket wheel 2 is driven by a driving means, whereby the endless conveyor belt 1 travels at a prescribed speed in the arrow direction as shown in FIG. 1. As shown in FIG. 2, each of the plurality of cooling metal members 4 has on the outer surface thereof a plurality of narrow and deep cooling grooves 3, of which the longitudinal direction is substantially parallel to the travelling direction of the endless conveyor belt 1. As shown in FIG. 2, a pushing board 4' having a length substantially equal to the length of the cooling groove 3 and having upset portions at the both ends is fitted to the bottom of each of said plurality of cooling grooves 3, so that one end of said pushing board 4' is inserted into the cooling groove 3 and the other end thereof projects from the back surface of the cooling metal member 4. The pushing board 4' vertically slides in the cooling groove 3 until any one of the upset portions at the both ends thereof reach the bottom surface of the cooling groove 3 or the back surface of the cooling metal member 4.
In FIG. 1, 7 is a molten slag container arranged above a point in the upstream of the upper forwarding position of the endless conveyor belt 1. The molten slag container 7 receives, for example, a molten slag 5 from a blast furnace (not shown) through a feeding trough 6. The molten slag 5 in the molten slag container 7 is poured through a pouring nozzle 7a provided at the bottom of the molten slag container 7 into the plurality of cooling grooves 3 of the cooling metal members 4 which are in travel, and rapidly cooled and solidified at a high cooling rate by the cooling metal members 4 forming the cooling grooves, substantially completely into a vitreous slag.
As shown in FIG. 1, when the cooling metal member 4 full of solidified vitreous slag 5' reaches a point in the downstream of the upper forwarding position of the endless conveyor belt 1, the pushing board 4' of the cooling metal member 4 is pushed into the cooling grooves 3 by a stripper 8 comprising rollers fixed to the inside of the endless conveyor belt 1, whereby the solidified vitreous slag 5' in the cooling grooves 3 is pushed out from the cooling grooves 3 in granular form and discharged onto the chute 9. The vitreous slag 5' discharged onto the chute 9 is received in a hopper 11 through a transfer conveyor 10. The empty cooling metal member 4 after removal of the vitreous slag 5' reaches the lower returning position of the endless conveyor belt 1 along with the travel of the endless conveyor belt 1, and at this position, the cooling metal member 4 is blown with cooling water from spray nozzles 12 and thus cooled to a prescribed temperature.
The above-mentioned apparatus for manufacturing a vitreous slag using an endless conveyor belt has a high cooling rate sufficient to substantially completely vitrify a molten slag. According to this apparatus, therefore, it is possible to manufacture a vitreous slag substantially completely vitrified which has an excellent quality as a cement material. The above-mentioned apparatus for manufacturing a vitreous slag using an endless conveyor belt has however a complicated structure, and it is very difficult, with this apparatus, to recover a high-temperature heat contained in the cooling metal members 4 through heat exchange with the molten slag.
To solve this diffculty, there has been proposed an apparatus for manufacturing a vitreous slag using cooling drums. FIG. 3 illustrates the apparatus for manufacturing a vitreous slag, which is substantially the same as the apparatus for manufacturing a vitreous slag disclosed in the U.S. Pat. No. 4,050,884 dated Sept. 27, 1977. More particularly, FIG. 3 is a schematic sectional view illustrating an embodiment of the apparatus for manufacturing a vitreous slag. In FIG. 3, 13 is an enclosed-structure housing. The housing 13 has an opening 13a at the top thereof for passing a molten slag, and a discharge port 13b at the lower end thereof for discharging a crushed vitreous slag. In the housing 13, a pair of cooling drums 14 with the same diameter and the same length are arranged so that the axial directions thereof are parallel to each other in the same horizontal level and the peripheral surfaces thereof are in contact with each other. Each of the pair of cooling drums 14 is rotated, by a driving means (not shown), in directions opposite to each other at the same peripheral speed, as shown by the arrows "a", "a'" in FIG. 3, i.e., in the rising direction of the peripheral surface thereof at the contact portion of the pair of cooling drums 14. A plurality of cooling through-holes (not shown) are pierced in the peripheral wall of each of the plurality of cooling drums 14 in the axial direction thereof. One end of each of the plurality of cooling through-holes communicates with the interior of a hollow portion (not shown) of one end of the center axle of the cooling drum, and the other end of the cooling through-holes communicates with the interior of a hollow portion (not shown) of the other end of the center axle of the cooling drum. The hollow portion (not shown) of the one end of the center axle of the cooling drum 14 is liquid-tightly connected, through a swivel joint (not shown), to one end of a pipe 42. The other end of the pipe 42 is connected to the inlet of a steam drum 18. An end of another pipe 44 provided with a pump 43 on the way is connected to the hot water outlet of the stream drum 18. In FIG. 3, 18a is an air feed valve and 18b is a water supply valve. The other end of the pipe 44 is liquid-tightly connected, through a swivel joint (not shown), to the hollow portion (not shown) of the other end of the center axle of the cooling drum 14. In FIG. 3, the steam drum 18 is connected to one of the cooling drums 14, but another steam drum (not shown) is similarly connected also to the other cooling drum 14. Therefore, cooling water for cooling the cooling drum 14 is supplied, through the pipe 44 and the axle in the peripheral wall of the cooling drum 14, to the plurality of cooling through-holes of the periphery of the cooling drum 14 by means of the pump 43. The cooling water supplied to the pluraity of cooling through-holes is heated by the heat contained in the molten slag 5 deposited onto the peripheral surface of the cooling drum 14 as described later and supplied, through the axle of the cooling drum 14 and the pipe 42, to the steam drum 18 while partially generating steam. The pressurized steam supplied to the steam 18 is separated, in the steam drum 18, into steam and hot water. The hot water separated in the steam drum 18 is supplied again, as the cooling water, to the plurailty of cooling through-holes in the peripheral wall of the cooling drum 14 through the pipe 44 by means of the pump 43. Thus, the cooling water circulates between the cooling drum 14 and the steam drum 18. The steam separated in the steam drum 18 is, on the other hand, used for driving, for example, a turbine (not shown).
A pair of weirs 16 are provided at the upper halves of the both ends of the pair of cooling drums 14 so as to be in contact with the both ends of the pair of cooling drums 14 (FIG. 3 shows only one of the pair of weirs 16). The top ends of the pair of weirs 16 are connected by a cover 16' having at the center thereof an opening 16'a. The pair of weirs 16 and the cover 16' are supported on the housing 13 by means of a supporting means (not shown). A slag sump 45 is formed by the bodies of the pair of cooling drums 14 and the pair of weirs 16. The molten slag 5 from a slag runner 15 is poured, through the opening 13a of the housing 13 and the opening 16'a of the cover 16', into the slag sump 45, where a slag pool is formed. The molten slag 5 poured into the slag sump 45 is deposited onto the peripheral surfaces of the cooling drums 14 during rotation, rapidly cooled and solidified, substantially completely into a vitreous slag. The cooling water supplied to the plurality of cooling through-holes in the peripheral wall of the cooling drum 14 is heated by the molten slag 5 deposited onto the peripheral surfaces of the cooling drums 14 into a pressurized steam. When the solidified vitreous slag 5' reaches the lower halves of the cooling drums 14 along with the rotation of the cooling drums 14, the vitreous slag 5' deposited onto the peripheral surfaces of the cooling drums 14 is peeled off therefrom, while being crushed, by a scraper 17 supported on the housing 13 by means of a supporting means (not shown), and drops into the lower part of the housing 13. An opening and closing means (not shown) is provided in the discharge port 13b of the lower part of the housing 13. The peripheral surfaces of the cooling drums 14 from which the vitreous slag 5' has been peeled off by the scraper 17 comes again into contact with the molten slag 5 in the slag sump 45 along with the rotation of the cooling drums 14, whereby a vitreous slag is continuously manufactured.
According to the above-mentioned apparatus for manufacturing a vitreous slag using cooling drums, it is possible to continuously manufacture a vitreous slag, and still recover a high-temperature heat contained in the cooling drums 14 through heat exchange with the molten slag. However, the above-mentioned apparatus for manufacturing a vitreous slag using a pair of cooling drums involves the following problems: Since water is supplied, as the cooling medium, to the cooling through-holes provided in the peripheral wall of the cooling drum 14, effective recover of a high-potential high-temperature steam requires conversion of the cooling water into steam with a very high pressure. Production of such a high-pressure steam in the cooling through-holes in the peripheral wall of the cooling drum 14 which is subjected to serious repetition of heating and cooling by the contact with the high-temperature slag pool in the slag sump 45 is not desirable in safety, because of the risk of cracking and explosion of the cooling drums after the lapse of a certain period of time. Furthermore, application of a high pressure to the swivel joint is not desirable from the practical point of view.
The molten slag deposited onto the peripheral surfaces of the cooling drums 14 in rotation is rapidly cooled and solidified into a vitreous slag. The vitreous slag thus obtained forms a layer with a prescribed thickness on the peripheral surfaces of the cooling drums 14, and remains in this state without being subjected to any constraint until it is peeled off from the peripheral surfaces of the cooling drums 14 by the scraper 17. Therefore, the vitreous slag deposited onto the peripheral surfaces of the cooling drums 14 is peeled off therefrom from while being crushed, by the scraper 17, and drops down. Very large pieces of vitreous slag sometimes drop into the lower part of the housing 13. As a result, the discharge port 13b at the lower part of the housing 13 is clogged, thus making it difficult to smoothly remove vitreous slag gathering in the lower part of the housing 13 through the discharge port 13b, and also making the subsequent handling more troublesome.